The present invention is a method for determining the cores or building blocks of a heavy hydrocarbon system. The invention also includes a method of generating parent molecules from the cores or building blocks. In a preferred embodiment, the heavy hydrocarbon is a vacuum resid. Cores or building blocks are defined as non-paraffinic molecular structures that are bridged by weak bonds that can be dissociated by the controlled fragmentation as described in this invention. Weak bonds include aliphatic carbon-carbon bonds and aliphatic carbon-heteroatom bonds. Examples of cores and building blocks are shown in FIGS. 37 and 38.
Petroleum oils and high-boiling petroleum oil fractions are composed of many members of relatively few homologous series of hydrocarbons [6]. The composition of the total mixture, in terms of elementary composition, does not vary a great deal, but small differences in composition can greatly affect the physical properties and the processing required to produce salable products. Petroleum is essentially a mixture of hydrocarbons, and even the non-hydrocarbon elements are generally present as components of complex molecules predominantly hydrocarbon in character, but containing small quantities of oxygen, sulfur, nitrogen, vanadium, nickel, and chromium. Therefore, in the present invention petroleum and hydrocarbon will be used interchangeably.
One way to obtain building block information is to perform detailed characterization of the vacuum gas oil (VGO) of the corresponding resid. There are a number of issues with this approach in addition to analytical cost and time required for detailed characterization. First of all, VGO molecules do not represent all cores existing in the resid. Certain larger aromatic cores (>6 aromatic rings) and multi-heteroatom molecules cannot be found in VGO. Secondly, the building block distribution of resid may not be the same as that in VGO.
A vacuum gas oil is a crude oil fraction that boils between about 343° C. (650° F.) to 537° C. (1000° F.). A vacuum residuum is a residuum obtained by vacuum distillation of a crude oil and boils above a temperature about 537° C.
Another way of determining resid core structure is to crack resid structure by thermal or other selective dealkylation chemistry. Coking is a major problem in the thermal cracking approach because of the secondary reactions. Thermal cracking under hydrogen pressure may yield less coking but can still alter the building block structure by hydrodesulfurization. Quantitative assessment of building block distribution is very challenging.
Significant progress has been made in the determination of molecular formulas of heavy petroleum molecules. However, for the same molecular formula, different structures can be assigned. Heavy petroleum value and processability can be heavily affected by the assignment of core structures. There is not an easy method to generate the building block distribution. The present invention can dissociate petroleum molecules inside a mass spectrometer without forming coke. Building block information can be determined by the measurements of fragment ions.